Testing: Longitudinal Chromatic Aberration and focus shift
Lenses with focal ratios of f2.8 or larger are often prone to longitudinal color aberrations (loCA, a.k.a. “axial color” or “Bokeh CA”). These normally show up as magenta coloration in the foreground and greenish hues in the background and are not easily corrected in post-processing. The Sony FE 35mm f2.8 ZA is not the best regarding loCA considering that it has a focal ratio of only f2.8. The following 100% crops show the foreground on the left and the background on the right with the first crop at f2.8 and the second at f4.0:
You can see the coloration around the background branches in the following example although the foreground does not show a prominent magenta halo:
The test also revealed that there is no focus shift to speak of.
Sharpness and contrast
Let’s have a look at the theoretical performance of the Sony FE 35mm f2.8 ZA first and compare it to some alternatives:
The MTF charts of the Zeiss (designed) lenses from Sony and Zeiss show the contrast wide open at 10 (red), 20 (green) and 40 line-pairs per mm (purple). The computed MTF chart of the Sigma 35mm f1.4 Art shows contrast at 10 lp/mm (red) and 30 lp/mm (green) at f1.4 without influence of diffraction. Higher values are better (more contrast) and the closer the solid and dotted lines are together the less astigmatism (= resolution depends on the orientation of the test-pattern) the lens has. The x-axis displays the distance from the optical axis (=center of the sensor) in mm. I’ll show you the real-life performance at 4 mm (center), 13 mm (APS-C-corner), and 20 mm (FF-corner) on a 42MP Sony A7R II body for the Zeiss designed lenses.
From the charts it is clear that the Sony 35mm f2.8 ZA and the Sigma 35mm f1.4 art have steep drops in contrast and resolution towards the full-frame corners. But other than that the different methodologies and the different focal ratios used in these charts makes it hard to compare the lenses. So let’s see how these lenses perform in my sharpness test based on Siemens-stars. Processing was done in Lightroom 8/CRAW 11 from RAW to Adobe Color profile with the built-in lens profile applied. Noise-reduction is set to 0, sharpening to 50/0.5/36/10, with no extra tone, color, or saturation adjustment. White-balance was adjusted to a neutral white and I did some exposure compensation to make the brightness of all crops match. So you will not see light fall-off in the corners.
The following 100% crops show the Sony FE 35mm f2.8 ZA from f2.8 down to f11 compared to the Sony 35mm f1.4 ZA and the Zeiss Batis 40mm f2.0 CF (all shot on a 42MP Sony A7R II) plus the Sigma 35mm f1.4 Art shot on a 36MP Nikon D800. Linear resolution of the D800 sensor is only 7% lower which should not make a distinct difference in this comparison but I increased sharpening to 70/0.5/36/10 to counteract the slightly softening effect of the AA-filter in the D800.
In the center all four lenses look very sharp at f2.8. At the APS-C-corner the Zeiss Batis looks best followed by the Sony FE 35mm f2.8 ZA, the Sony FE 35mm f1.4 ZA and the SIgma Art. The full-frame corner looks best on the Zeiss Batis and the Sigma Art with the f1.4 Sony and the f2.8 Sony clearly trailing behind.
Let’s see how the Sony FE 35mm f2.8 ZA develops when stopped down further:
Within the APS-C image-circle the Sony FE 35mm f2.8 ZA looks very good from f4.0 onward, while the FF-corner needs stopping down to f5.6 or even f8 to become moderately sharp.
Overall the comparison shows that the Sony FE 35mm f2.8 ZA is pretty good in the APS-C image-circle but lacks well defined full-frame corners.
Performance at long distances
The Siemens-star test-targets are shot at a distance of 45x focal length (i.e. at around 1.6m). But as performance of lenses also depends on the shooting distance I did another series of test-shots of a city around 1 km away. Processing was done in Lightroom 8/CRAW 11 from RAW to Adobe Color profile with the lens-profile automatically applied. Noise-reduction is set to 0, sharpening to 50/0.5/36/10, with no extra tone, color, or saturation adjustment. I used autofocus at the largest aperture and did not change focus for other apertures.
The main image shows the complete scene wide open to give you an impression of the angle of view and to judge vignetting. You can access the respective shots up to f11 via the links beneath the main image. Following the main image are 100% crops from the Sony FE 35mm f2.8 ZA down to f11 compared to the Sony 35mm f1.4 ZA and the Zeiss Batis 40mm f2.0 CF (all shot on a 42MP Sony A7R II) at f2.8. All lenses were shot on the same day only minutes apart.
You can click on each image to access the large original. Please respect our copyright and only use those images for personal use.
The Sony FE 35mm f2.8 ZA trails the other two lenses in this comparison with a slightly softer rendering. I also had to take the other diagonal of the image in this comparison, as the little lens was quite decentered.
Following is how the Sony FE 35mm f2.8 ZA develops when stopped down:
Stop down to f5.6 and the Sony FE 35mm f2.8 ZA produces a pretty sharp image across the full-frame sensor.
Rendering of point-light sources at night-shots
Night-shots pose a different challenge for lenses as the contrast is even higher than under bright sun and point-light sources can reveal some weaknesses such as coma, haloing and color-aberrations that do not show up as prominently in other test-shots. The 100% crops below the main image show the effect of coma in the FF-corner of the Sony 35mm f2.8 ZA, Sony FE 35mm f1.4 ZA, and the Zeiss Batis 40mm f2.0 CF at various apertures:
The Sony FE 35mm f2.8 ZA shows the strongest coma of the lenses compared here at f2.8 while the Sony FE 35mm f1.4 ZA is the best here with practically no coma at f2.0 already.
Rendering of out-of-focus point-light sources
This test is for the rendering of point-light sources in an out-of-focus background. The circle of confusion that is produced by this test is pretty indicative of Bokeh performance (in the background) and light fall-off. Ideally the out-of-focus image of the point-light is evenly lit and perfectly circular, with no “onion-rings”, and without coloration. Large aperture lenses normally produce an effect known as “cat’s eye” the further away from the optical axis the point-light is projected. This is due to optical vignetting in the lens barrel when light enters the lens from an angle.
Of the three lenses in this comparison the Sony FE 35mm f1.4 ZA clearly produces the largest Bokeh balls with only a little outlining and weak onion rings. The Sony FE 35mm f2.8 ZA shows very visible onion-rings and a bit stronger outlining. Due to its f2.8 focal ratio the Sony FE 35mm f2.8 ZA has 50% smaller Bokeh balls in the center compared to its f1.4 sibling. The Bokeh balls of the Zeiss Batis should be only 20% smaller in the center compared to the Sony FE 35mm f1.4 ZA but the difference is overstated in the image above as I did not set the focus on the Zeiss Batis correctly for this comparison. The Zeiss Batis also shows strong onion-rings and outlining. Compression of the Bokeh balls is visible in the APS-C-corner already with both Sony lenses producing the typical cat’s eye while the Zeiss Batis retains a more circular form.
Let’s see how this analysis of out-of-focus point-light sources translates into Bokeh-performance shooting a book-shelf.
From the comparison above it is clear that the larger focal ratio (potentially) produces the better Bokeh: The Sony FE 35mm f1.4 ZA leads in this comparison. The Zeiss Batis is already hampered by its f2.0 focal ratio and shows some outlining in the background. Last comes the Sony 35mm f2.8 ZA which simply cannot compete with the others in this comparison.
The Sony FE 35mm f2.8 ZA goes only down to 1:7.5 magnification which is the worst of the lenses compared here. Its close-up performance is usable within the APS-C image-circle once you stop down to f5.6 or beyond. The following image was shot at 1:8 magnification where the area of sharp focus is 192 x 288mm. The crops shown below are (from left to right) from 2mm, 6mm, and 12mm off the center of the sensor respectively:
Btw.: At these distances the lens develops strong pincushion distortions.
Flare, ghosting, and sun-stars
Catching a strong light-source shining directly into the lens is always a risky business: it could produce strange colorful ghost-images or reduce contrast considerably through flare and glare. The appearance of flare and ghosting depends on factors like the aperture and the angle of the light hitting the lens. So to judge the proclivity of the Sony FE 35mm f2.8 ZA for these artifacts I went through a series of well calculated shots against a strong light source to provoke glare and ghosting.
The Sony FE 35mm f2.8 ZA shows only little flare and ghosting. The following image at f11 is one of the most obvious examples:
The little square inset in the upper left of the image shows the respective area with an exposure compensation of +3 EV to make it easier to see which levels of black the lens renders at that point. It shows that the Sony FE 35mm f2.8 ZA renders a pretty deep black against contra light. But when the light-source is just outside the corner there is a very obvious resulting streak. Fortunately this only happens in a very small area around the corners:
All-in-all the Sony FE 35mm f2.8 ZA let’s you shoot confidently under adverse contra-light situations as long as you avoid strong light-sources just outside the corners.
If you want to produce pretty sunstars stop the lens down to f8.0 at least as sunstars from this lens are not too impressive at f5.6 or below:
Next check out my sample images!Check prices on the Sony FE 35mm f2.8 ZA at Amazon, B&H, Adorama or WEX! Alternatively get yourself a copy of my In Camera book or treat me to a coffee! Thanks!